Pawl arrangement

ABSTRACT

This application discloses an improved mechanism for watches comprising a brush in a pawl arrangement which functions to prevent backward movement of an index wheel which is advanced stepwise by a pawl actuated in turn by a vibrating member, such as a mechanical resonator, operating at an audio frequency. The functions of the pawl and brush can be reversed. The index wheel can be radially magnetized, or mounted on a radially magnetized arbor to provide magnetic coupling to a dial train.

United States Patent Inventor App]. No.

Filed Patented Assignee Priority PAWL ARRANGEMENT 27 Claims, 15 Drawing Figs.

U.S. Cl

58/23 V, 58/116 M, 74/577 M, 74/575, 74/123 Int. Cl ..Fl6h 27/112, G04c 3/00 Field of Search 58/23 D, 116,116 M, 122,23 V; 74/142,575, 128, 577

References Cited UNITED STATES PATENTS 9/1926 Burstyn 4/ 1940 Bott 6/1969 Hetzel i.

FOREIGN PATENTS 5/1909 Great Britain 4,

2/1966 France Primary Exa'miner-William F. ODea Assistant Examiner-Wesley S. Ratliff, Jr. Attorney Stevens, Davis, Miller & Mosher ABSTRACT:

This application discloses improved mechanism for watches comprising a brush in a pawl arrangement which functions to prevent backward movement of an index wheel which is advanced stepwise by a pawl actuated in turn by a vibrating member, such as a mechanical resonator, operating at an audio frequency. The functions of the pawl and brush can be reversed. The index wheel can be radially magnetized, or mounted on a radially magnetized arbor to provide magnetic coupling to a dial train,

x If PATENTEU AUG] 7 ran PAWL ARRANGEMENT The invention relates to a pawl drive arrangement for converting a mechanical vibration into a unidirectional rotary movement, with an index wheel, a pawl unilaterally engaging the teeth of the index wheel, and a friction drive resting on the index wheel particularly for timepieces having as the regulating organ a mechanical resonator operating at an audio frequency and that is mechanically connected to a motion work, or dial train, by the pawl drive arrangement.

Swiss Pat. No, 3l8,230, US. Pat. No. 2,908,l74, French Pat. l,l50,879, British Pat. 8 19,3 64, and Federal German Pat. 1,037,972 all disclose a drive pawl arrangement for watches, the running of which is controlled by a mechanical resonator carrying a driving pawl that engages the teeth of an index wheel, said index wheel being braked in its rotation by a stationary brake. In these heretofore known drive pawl arrangements, the stationary brake equally resists movement of the index wheel in either direction. In order to function properly, the resistance of the brake must be greater than the tangential component of the force of the driving pawl resting on a gently sloping and flat tooth back and greater than the frictional force between this pawl and the tooth back, when the resonator withdraws the driving pawl. This same braking resistance, however, must also oppose turning of the index wheel under the effect of an impulse from the driving pawl, when the resonator causes the latter to strike the steep contact face of a tooth. Consequently, the friction between the brake and the index wheel is very large in the prior art drive pawl arrangement. Bad wear resistance properties, high-energy consumption, and unreliable operation are other disadvantages of these prior art constructions.

There are known drive pawl arrangements having a holding jack that rectifies, within certain limits, the rotation of an index wheel driven by a driving pawl. The drive arrangements operate relatively dependably, provided that the positions of the holding jack and the driving pawl relative to each other and to the teeth of the index wheel are precisely adjusted. An important drawback of these arrangements is that the adjustment of the jack and pawl positions requires relatively expensive jack and pawl mounts and adjustment devices, as well as a great deal of precise mechanical work performed by specialists. Moreover, these known arrangements, incorporating a holding jack and a driving pawl, fail in operation if the frequency of the oscillatory movement, which must be converted into unidirectional movement, is too high. The highest such frequency hitherto in Wristwatches was 720 c./s. If the jack and pawl of this known arrangement are to respond to each and every oscillatory movement, as is customarily the case with watches, the driving pawl, after each of the impulses it gives to the index wheel, must turn the index wheel backwards until the steep face of a tooth strikes the holding jack and stops the wheel. Only this requirement can ensure that the sum of the forward movements of the index wheel is precisely determined by the oscillations of the driving pawl. Aside from the adjustment of the phase relationship between the jack and pawl, the necessary return movement of the index wheel, which latter steps forward and then part ways backward, would create insoluble problems at high frequencies.

The purpose of the invention is to provide a pawl arrangement, particularly suited to watches, which overcomes the aforesaid disadvantages, which is simple in construction, dependable in operation, easy and inexpensive to manufacture, and which does not require extensive timing before it is ready for use.

A chief object of the invention is a pawl arrangement for watches having as the regulating organ a mechanical resonator working at a very high frequency, i.e., 1,000 c./s. and higher, the oscillations of the resonator being mechanically converted into a rotary movement and transmitted to the motion work, or dial train.

The pawl arrangement of the present invention permits the construction of watches having mechanical resonators that operate at 1000 c./s. and higher. With this range of frequencies it was hitherto virtually impossible in watches to convert the oscillations into rotation, since it was impossible with prior art constructions to adjust the phase relationship between the pawl ad the jack with the necessary accuracy.

The objects of this invention are achieved by using a brush as the friction device in a pawl arrangement. The brush is so located that its bristles lie on a plurality of the gently sloping backs of the teeth of the index wheel and extend towards the steep faces of the teeth so as to offer no resistance to movement of the index wheel in the impulse direction of the pawl, but a very great resistance to movement in the opposite direction. The pawl preferably serves as a driving pawl and is connected to a driving member, and the brush is constructed as a stationary brake, which offers no, or at least only very lit tle, resistance to rotation in the impulse direction of the driving pawl, but offers a very high resistance in the opposite direction. The brush thus acts to permit movement in only one direction. The pawl arrangement of the invention can also be used in its reversed form, the brush being connected to a driving member and the pawl, stationary, preventing reverse movement of the index wheel.

An appreciation of the breadth of the present invention can be had by consideration of various embodiments thereof in conjunction with the annexed schematic drawings wherein:

FIG. I is a fragmentary side view of one embodiment of the pawl arrangement of the invention, the pawl being connected to the vibrating member of a mechanical resonator and the brush serving to prevent backward movement of the index wheel;

FIG. 2 is a fragmentary side view of a modification of the embodiments shown in FIG. I, the pawl and brush playing reversed roles;

FIG. 3 is a fragmentary side view of another embodiment;

FIG. 4 is a fragmentary front view of still another embodi ment;

FIG. 5 is a fragmentary perspective view of a pawl arrangement with a rectangular parallelepiped pawl stone;

FIG. 6 is a perspective view of part of a pawl arrangement having a triangular-prism pawl stone;

FIG. 7 is a perspective view of part of a pawl arrangement equipped with a semicircular-cylindrical pawl stone and a suitable index wheel;

FIG. 8 is a view in cross section taken along line VIII-VIII of FIG. 7;

FIG. 9 is a fragmentary front view of a pawl arrangement particularly intended for use in watches with resonance drive and magnetic coupling;

FIG. 10 is a front view ofa modification of the embodiment shown in FIG. 9;

FIG. 11 is a cross-sectional view of a pawl arrangement of the invention mounted in a timepie FIG. 12 is a cross-sectional view of a modif tion of the embodiment shown in FIG. 11',

FIG. 13 is a top view of part of the arrangement shown in FIG. 12;

FIG. 14 is a view in cross section taken along line XIV-XIV ofFIG. l2; and

FIG. 15 is a cross-sectional view of a portion of a form for making the bristles for the brush friction device of the present invention.

With reference to the embodiment shown in FIG. 1, the individual filaments I, 1', etc., are bound together at one end like mechanical bristles of a brush. The free ends of these filaments, or bristles, consequently spread apart and must be suitably cut to ensure their correctly contacting the teeth faces of the index wheel 2. The angles at which the different filaments contact these faces are not the same however.

The index wheel 2 is driven by a pawl 3 having a pawl stone 4 and fixed to the arm 5 of a mechanical resonator.

The embodiment shown in FIG. 2 corresponds to that shown in FIG. 1. the filaments 1a, the index wheel 2a, the pawl Saand its stone 4a, and the arm 5a being similar in construction to the corresponding parts in the previous embodiment. But in this case the filaments la are fixed to the oscillating arm 50, whereas the pawl 3a is mounted on a stationary part.

FIG. 3 shows an index wheel 6, a pawl 7 with its stone 8, and a holder 9 for the filaments l0, 10'. In this embodiment, as in the two previous ones, either the pawl 7 or the filaments l0, l0 are fixed to the oscillating member of a mechanical resonator.

It is characteristic of the embodiment shown in FIG. 3 that the different filaments 10, 10' contact the teeth of the index wheel 6 at approximately the same angle. The free ends of the filaments consequently converge towards each other.

The free ends of the filaments of the embodiments shown in FIGS. 1, 2, and 3 can be so cut that they define the surface ofa circular cylinder having a diameter equal to the mean diameter of the index wheel.

The fourth embodiment shown in FIG. 4 has an index wheel 13 on a shaft 14, and a stationary or oscillating part 11 mounting the bristles, or filaments 12, 12', etc. The pawl that forms part of the combination is not shown.

If the index wheel 13 is made very thick so that the teeth are very wide, it is apparent that it can be advantageous to cut (as shown in FIG. 4) the free ends of the bristles diagonally with respect to the generatrix of the cylinder defined by the teeth of the index wheel, or otherwise to cut the bristles straight and to set the brush composed by the bristles at an angle. In this way. the individual free bristle ends contact the index wheel teeth at different angular positions measured along the circumference of the wheel.

From the foregoing it is apparent that the brush can consist of a plurality of bristles arranged next to, or behind, one another, each bristle being located in a different position with respect to the index wheel teeth to ensure virtually that the free end of at least one bristle is positioned at the steep face of a tooth of the index wheel in virtually all positions assumed by the wheel during operation. The brush can consist of a large number of bristles, the individual positions of which bristles are not precisely determined. Even if the individual bristles take different positions with respect to each other, the number of bristles need not be large. Even with relatively few bristles the position of the individual bristle with respect to the index wheel does not play an important role. The brush functions as a very nearly ideal movement rectifier, which prevents movement in one direction and allows completely free movement in the other.

The bristles of the brush, at where they touch the index wheel, should preferably make an average angle of 100 to I40, particularly about I, with the radius of the index wheel. The brush advantageously covers at least two teeth, and preferably half of all the teeth of the index wheel. The number of teeth that must be covered depends to a very great extent on the number of bristles that can be brought to bear on a unit length of the index wheel circumference. Where the index wheel and the brush are very thick, the brush need cover only a relatively few teeth. But if the index wheel is relatively thin and the brush correspondingly narrow, the bristles must engage a correspondingly larger number of teeth at the same time.

It is particularly in Wristwatches that the pawl drive arrange ment, having a driving pawl connected to the mechanical resonator, must avoid large inertial forces. The motion work, or dial train, driven by the pawl arrangement, represents a large mass that would act with very great force through the driving pawl, were the transmitted oscillations of a high frequency.

For this reason, it has been suggested (Swiss patent application l2,53l/65) to use with the pawl arrangement a loaded spring for smoothing out the flow of energy. A purely magnetic coupling in a drive pawl arrangement is also known (Swiss patent 457,295

FIG. 5 shows a particular embodiment of a pawl. In the embodiments illustrated in FIGS. 1-4, a pawl stone in the shape of a rectangular parallelepiped is so fixed on the pawl that a longitudinal edge engages the teeth of an index wheel. The index wheel, however, was considerably thinner than the pawl or its stone. But if the index wheel is very thick, the longitudinal edge of the pawl stone would have to be set exactly parallel to the teeth edges, a condition that is very difficult to satisfy. In accordance with the embodiment shown in FIG. 5, the rectangular parallelepiped pawl stone 15, which can be a ruby, for example, is fixed diagonally on a projection 16 of the pawl 17, so that a corner edge 18 acts on the teeth of an index wheel 19.

Experience has shown that the pawl stone clings to every available rigid surface because of surface stresses that appear when it is being fixed to the bent elastic projection 16, using a self-hardening synthetic resin plastic, such as that known under the registered trademark Araldit. If the pawl stone is to be mounted diagonally as shown in FIG. 5, it must, therefore, be held fast while the synthetic resin plastic is setting.

To overcome these difiiculties, an approximately triangularprism stone 20 is used, as illustrated in FIG. 6. The pawl in this figure corresponds to that seen in FIG. 5.

In the embodiment illustrated in FIGS. 7 and 8, there is used a semicircular-cylindrical pawl stone 21 that engages the similarly cylindrically concave teeth 22 of an index wheel 23. Since the surfaces of the teeth 22 are not flat, the pawl 24 cannot slip off the index wheel 23 even under the effect of shocks.

The technology required to fix a stone in this new way on the pawl is not simple. For production, a triangular-prism stone is preferred. A stone of this shape so positions itself, during cementing, on the end of the pawl that a corner edge of the stone acts as a projection of the pawl and contacts the index wheel teeth.

The pawl arrangement of the invention can also incorporate magnetic coupling which mechanically separates the index wheel from the subsequent motion work and comprises two magnet wheels, one of which is fixed coaxially to the index wheel. The other magnet wheel, magnetically coupled to the first, can be made as much larger than the index wheel as desired. The magnetic coupling acts as an energy store that smooths out the discontinuous movements of the index wheel with respect to the motion work. The latter, consequently, despite its relatively large mass, opposes the driving pawl with very little inertial force.

In accordance with a particular embodiment of the invention, the index wheel is also a magnet wheel having pole pairs with alternating polarity around the wheel circumference and radially outwardly extending fields. A second magnet wheel can be magnetically coupled to the index wheel.

For use in small Wristwatches it has proved particularly advantageous to mount the index wheel on an arbor of high magnetic retentivity that has several pairs of poles with alternating polarity on its circumference and which is coupled magnetically to a magnet wheel. The arbor "n, for example, have one or two pairs of poles.

In view of the dimensions of the known pawl arrangements, it is apparent that a brush cannot be used to brake the index wheel. Because the latter is so thin, the bristles of the bin. would slide on the sides of the index wheel. Nor could the brush, for preventing reverse movement, act on the magnet wheel of the known pawl arrangement, b cause the difference in the diameters of the two wheels would magnify even the slightest (between the brush and the magnet wheel) opposite to the impulse direction of the driving pawl on the index wheel. In one embodiment of the invention, therefore, the index wheel of the pawl arrangement for a wristwatch has a diameter of about 0.4 to l mm., preferably approximately 0.6 mm., and a thickness of about 0.3 to 0.05 mm., preferably approximately 0.15 mm. It then has about the same outer dimensions as the magnet wheel on the same arbor.

Since the index wheel of the pawl arrangement of the invention is about five times as thick as the index wheel of a known pawl drive arrangement for the same purpose, the bristles of a brush no longer slide on the sides of the index wheel but instead rest on the gently sloping backs of the index wheel teeth. Inasmuch as the index wheel in the invention has only about one-fourth of the diameter of a known index wheel for the same purpose, it has a for smaller moment of inertia than the latter wheel. In order to recognize the great significance of these masses for a pawl arrangement for a wristwatch, it must be understood that in a specific application. such as the drive for the motion work, or dial train, the power generated by the pawls and bristles of a pawl arrangement is proportional to the third power of the frequency at which the index wheel receives impulses. The frictional forces in the motion work, for example, are completely insignificant at high frequencies. In a watch having a mechanical resonator, and a drive pawl arrangement with the dimensions of these arrangements of the prior art, the power generated by the drive pawl arrangement would be far too great were the resonator to operate at a frequency of about I000 c./s. In the pawl arrangement of the invention the inertial forces are so very small that a maximum frequency higher than about 2000 c./s. can be expected.

FIGS. 9 and I0 show two embodiments of a magnetic coupling of the pawl arrangement.

In FIG. 9 are shown an index wheel 26 and a neighboring magnet wheel 27 arranged on a single shaft 25. In the plane of the wheel 27 is positioned a larger magnet wheel 28, magnetically driven by the wheel 27. The bristles and the pawl for the index wheel 26 are not shown.

In the embodiment illustrated in FIG. a shaft 29 mounts an index wheel 30 which is also constructed as a magnet wheel magnetically driving a larger magnet wheel 31 positioned in the same plane.

The dimensions are very important, the index wheel in FIGS. 9 and 10 having, in accordance with the invention, the same thickness and about the same diameter as the magnet wheel in a watch.

FIG. 11 shows part of a watch movement having a bottom plate with a blind hole 33. Two ruby bearings 34 and 35 arranged in this hole support a singly magnetically polarized arbor 36. A magnetized piece of metal 37 attracts the arbor 36 downwards, and a nonmagnetized opposed bearing 38 holds the other end of the arbor.

The arbor mounts an index wheel 39, and the bristles 41 are fixed to a part 40 of the plate 32. The pawl is not shown.

The rotation ofthe arbor 36 is magnetically transmitted to a magnet wheel 42.

In the embodiment for a watch, shown in FIG. 11, the arbor 36 of the index wheel 39 is preferably made of Plalinax or of another material of high magnetic retentivity. The teeth of the index wheel are preferably milled out of a copper-berylliumbronze alloy.

It has been observed that the necessary cutting tools are subjected to about three times the amount of wear if the index wheel teeth are milled out of Platinax instead of the copperberyllium-bronze alloy. Since the tools are diamond milling cutters, these expensive tools must be periodically replaced.

The embodiment illustrated in FIG. 11 presents no difficulties during manufacture, because the arbor 36 of Plarinax can be fabricated by a single grinding operation that does not require expensive tools. Moreover, the Platinax arbor 36 is very simply designed, and does not embody special pivots for the bearings. The diameter of the arbor 36 is 0.3 mm. and that of the index wheel 39 is approximately between 0.5 and 0.6 mm.

The index wheel arbor 36 is transversely magnetized and has one or two pairs of poles on its circumference. The piece 37 is sufficiently magnetized to hold the index wheel 39 in position as long as an axial acceleration in one direction does not exceed ten times the acceleration due to gravity. To ensure that an accelerative force cannot throw the index wheel out of its magnetized bearing, a supporting bearing 38 of nonmagnetic material is arranged above the wheel 39.

The magnet wheel 42 is not positioned in the same plane as the index wheel 39. The plate 32 is about l.5 mm. thick, enabling the sizes of the other parts to be estimated.

In the embodiment shown in FIG. 12, the magnet wheel 42' is now moved into the plane of the index wheel 39', and is magnetically coupled, as before, to the index wheel or to its arbor. Since the thickness of the index wheel 39' does not exceed about 0.015 mm., the magnet wheel 42' can be arranged sufficiently closely to the index wheel arbor 36' for the magnetic coupling. The thickness of the plate 32 in this embodiment is also about 1.5 mm.

The bearings for the index wheel embody all of the characteristics known in the watch industry for similar such bearings. However, a piece 37 or 37' of iron or nickel is placed at the end bearing to short circuit the magnetic field of the arbor 36 or 36' and thus to hold the latter in place.

The bristles, or filaments, 4] or 41 of the watch pawl arrangements, illustrated in FIGS. II and 12, are fixed to the bottom plate 32 or 32' and surround about half of the circumference of the index wheel 39 or 39', as schematically shown in FIG. 13. This means, of course, that all of the bristles lie in about the same plane and that there are, altogether, not a great many bristles to form the brush. Since in the strict sense a statistical distribution of the individual bristles is not possible, they must have a certain arrangement with respect to each other. To this end, the bristles lie in V-shaped grooves 40a, which precisely determine the direction of each bristle. The grooves 400 and the bristles 4] are illustrated in FIG. 14. A hardening casting material holds the bristles in the grooves.

It is particularly in those watches having a regulating organ operating at a very high frequency, such as 1000 to 2000 c./s., that the driving pawl is not provided with a stone. The pawl stone possesses a relatively large mass, causing the oscillatory system, consisting of the pawl spring and the pawl stone, to have a natural frequency of about 5000 c./s. A natural frequency this low would affect the operating frequency at about 2000 c./c., of the resonator. Without a stone the driving pawl has a very much higher natural frequency, which does not adversely affect the frequency of the resonator.

As previously remarked, the index wheel in the pawl arrangement of the invention should not be free to turn backwards. To this end, the driving pawl must not press so hard on the index wheel teeth that the wheel is temporarily moved part way backwards. The driving pawl in a wristwatch should transmit about I microwatt of power, corresponding to an impulsive force of 10 dynes in the longitudinal direction. A straight piece of tungsten wire having a diameter of 0.0] mm. will transmit approximately 10 times this force in the longitudinal direction before it bends. The bristles of the pawl arrangement, and the driving pawl itself, are preferably made of this kind of wire.

Moreover, since the wear on the driving pawl and on the free ends of the bristles is commensurate with the forces that must be transmitted and very mall, it has proved unnecessary to prolong the working life with a wl stone. At high frequencies, moreover, the additional forces due to t]. mass of the stone would instead lead to considerably increased wear.

Where the index wheel, as shown in FIGS. I1 and i2, is overhung and magnetically held, the wheel, of course, is 'v easily set in position and removed. With hitherto known (Living pawl arrangements in watches, a similarly simple construction was completely inconceivable.

In a particularly advantageous embodiment of the invention in a wristwatch having a mechanical resonator, the pawl is connected to the resonator and the motion work is magnetically coupled to the index wheel, the latter is mounted overhung on an arbor of high magnetic retentivity, and this arbor is prevented from moving axially by a magnetic end bearing. In accordance with the invention, this arbor is magnetized with at least one radially acting pole pair and is attracted against the mechanical stop of the magnetic end bearing, which has a piece of material of good magnetic permeability. A magnet wheel, connected to the motion work, is magnetically coupled to this arbor. The magnet wheel preferably lies in the same plane as does the index wheel, and is separated from the latter by a narrow space. The diameter of the index wheel is only a few hundredths of a millimeter greater than that of its arbor. The magnetic coupling between this arbor and the magnet wheel is therefore ensured. The particular advantage of this embodiment is that the entire pawl arrangement, including the magnet wheel, can be mounted in the open on a base plate, and therefore is easily inspected and worked on.

The index wheel frequently consists of a copper-beryllium alloy, and the arbor of Platinax II (trademark), an alloy comprised of 76.7 percent platinum and 23.3 percent cobalt. In accordance with the invention, the brush of the pawl arrangement consists of between approximately l and 40 bristles, preferably about 20, that lie approximately in a common plane and are distributed uniformly about a part of the circumference of the index wheel, The number of bristles divided into the number of index wheel teeth covered by the bristles does not yield a quotient that approaches an integral number. For example, brush bristles are so distributed over about 70 to 80 teeth of an index wheel having 160 teeth that the bristle ends, referred to the tooth pitch, divide the pitch into about 20 parts. Consequently, the index wheel is free to turn backwards only one-twentieth ofa tooth pitch, which in a practical sense is equivalent to an ideal movement in only one direction.

In manufacturing the pawl arrangement of the invention, particularly in fabricating the brush, considerable technological difficulties arise, of course. In respect of the brush, these difficulties can be surmounted by using, for the bristles, a filament of elastic material that is freely stretched so as not to touch another body, heated and cooled to remove internal stresses and to produce a straight filament, and then cut into lengths for the individual bristles, which are combined to make a brush. The filament can be made of glass or tungsten, for example. The filament is advantageously wound onto a coil form, heated to remove the internal stresses, and the individual straight lengths cemented together at one spot and the loops cut apart at another spot. Tungsten wire must be heated to 2600 C., resulting in recrystallization of the wire. The bristles can also be prepared individually and combined to form a brush. in this case, a filament is unwound from a first drum onto a second drum and heated in between the drums. The cooled filament is unwound off the second drum, cut to bristle length, and the lengths are combined into a brush.

A number of bristles can be combined and cast with one end exposed in a casting compound that is allowed to set, whereupon the exposed bristle ends are ground. Before casting, the bristles can be already combined into a brush or they can be temporarily bundled together. After grinding, the casting compound is dissolved in a solvent to set the bristles free. The grinding produces on the bristle ends very sharp edges that dependably engage the teeth of the index wheel. Where the bristles are already combined to form a brush before the grinding, the body of the brush, which holds the bristles, must, of course, not dissolve in the casting compound solvent.

If two winding drums are usedthe one braked and the other driven by a motor-the one drum can be wound with tungsten wire, which, if it were cut into short lengths, would not, however, give the required straight bristles. The tungsten wire, therefore, is unwound from the one, and wound onto the other, drum, the wire between these two drums being heated in a vacuum to a temperature of approximately 2600C. by an electric current, which is furnished to both drums. Before the wire comes to lie on the other drum it has already greatly cooled off and possesses a high degree of elasticity. Since the bends in the wire on the other drum do not exceed the elastic limit of the wire, the wire, after being unreeled off this other drum, again extends straight.

The individually cut bristles from such tungsten wire can be collected in a V-shaped holder, arranged parallel to each other, and then covered with a casting material that is allowed to harden. After casting, the ends of the bristles can be ground, producing sharp edges that engage the index wheel teeth well. Once the ends are ground, the casting material is dissolved in a solvent and the individual bristles freed.

A bristle thus made is laid in each of the grooves 400 shown in FIG. 14, and fixed in place by a casting resin that cures.

While placing the bristles 41 in the grooves 400, the index wheel 39 is replaced by a cylinder to facilitate correct mounting of the bristles. The mean diameter of this cylinder is somewhat less than that of the index wheel. The cylinder also incorporates teeth. When the bristles 41 are laid in the grooves 40a, they are drawn out until their ends touch the contact faces of these teeth. In this manner the bristles are given with respect to each other a relatively precisely defined position, The cylinder has fewer teeth than does the index wheel.

FIG. [5 illustrates another method for obtaining a suitable brush of bristles for the pawl arrangement of the invention.

Two metal members 44 and 45 and an electrically insulating spacer 46 form a cylindrical coil form held together by a screw 47. The piece 46 is sized so as to leave a path between the metal members 44 and 45, which are connected to a source of current U.

The generally circular cylindrical coil form enables the making of a brush having generally parallel bristles. The tungsten wire 47 is wound onto the form, and is temporarily cemented at some spot, such as 48, whereupon it is heated and annealed by the current from U. Once the tungsten wire has cooled ofi, it is removed from the coil form by cutting away the cemented spot 48 and cutting out those lengths of the wire that lay freely on the form. After the method is finished, only these lengths are used to make the bristles of the brush, which approximately takes the form shown in FIG. 14.

A suitable brush for the pawl arrangement of the invention can also be made using arrangements that are known in a similar form in weaving.

The bristles can also be made of animal organs, preferably the parts ofinsects, such as insect hairs.

The diameter of the bristles should not exceed 0.01 mm., and is preferably less.

The diameter of the index wheel in the embodiment of H6. 12 does not exceed that of its arbor by more than between about 0.03 and 0.3 mm., and preferably by about 0.10 mm.

The drums and coil forms used for winding the filament to prepare it for making the bristles can have guide grooves to prevent the wound filament from slipping off.

At least one of the members 44 and 45 of the coil form illustrated in FIG. 15 advantageously has a cutting edge.

When using two drums, the drum onto which the filament is wound from the other drum is approximately a circular cylinder and sufficiently large in diameter to ensure that the wound-up filament is not bent beyond its elastic limit.

Although the best embodiment of the present invention now known has been illustrated and described as well as numerous modifications thereof, it is to be understood that the inclusion of these modifications is solely for the purpose of demonstrating the breadth of the invention. It In therefore recognized that many species or modifications of the invention wnl -h have not been illustrated or described herein are nevertheless comprised within the scope of the appended claims.

I claim:

1. Apparatus for converting a mechanical vibration lnlo a unidirectional rotary movement, particularly suitable for timepieces of the type having as the egulating organ a mechanical resonator operating at an audio frequency connected to a dial train, comprising a toothed index wheel having teeth with gently sloping backs and steep contact faces, a pawl coacting with said teeth, a brush comprising a plurality of bristles that rest on a plurality of said teeth backs and are directed towards, and cooperate with, said teeth contact faces, a mechanical resonator operative at an audio frequency, said pawl being connected to said mechanical resonator to turn said index wheel step by step in a desired direction and said brush being arranged with respect to said index wheel so as to offer negligible resistance to angular displacement of said wheel in the desired direction but substantially to prevent angular displacement thereof in the opposite direction, a dial train magnetically coupled to said index wheel, an arbor of high magnetic retentivity for said index wheel, said index wheel being mounted to overhand on said arbor, and a magnetic end bearing for magnetically preventing axial movement of said arbor.

2. Apparatus as defined in claim l, further comprising magnetic pole pairs on said index wheel with alternating polarity around the wheel circumference and radially outwardly extending fields, and a magnet wheel magnetically coupled to said index wheel.

3. Apparatus as defined in claim 2, wherein said index wheel has two or three pole pairs.

4. Apparatus as defined in claim 1, wherein said arbor is radially magnetized to have one pole pair, and a magnet wheel magnetically coupled to said arbor.

5. Apparatus as defined in claim 1, wherein said brush bristles make an average angle of 100 to M, with the radius of said index wheel at the points of contact between said bristles and said index wheel.

6. Apparatus as defined in claim 5, wherein said brush bristles converge.

7. Apparatus as defined in claim I, wherein the entirety of the bristle ends define part of a virtually circular cylinder having a diameter approximately equal to the mean diameter of said index wheel.

8. Apparatus as defined in claim 7, wherein said brush covers about half of all of the index wheel teeth.

9. Apparatus as defined in claim 1, wherein said brush covers at least two teeth of said index wheel.

10. Apparatus as defined in claim 1, further comprising a substantially rectangular parallelepiped stone so arranged on said pawl means that a diagonal of said stone is directed towards said pawl, whereby a corner of said stone cooperates with said contact face of an index wheel tooth.

11. Apparatus as defined in claim 1, further comprising a triangular-prism stone so arranged on said pawl that a corner edge of said stone is directed towards, and contacts the teeth of said index wheel.

12. Apparatus as defined in claim 1, wherein said arbor is magnetized to have at least one pole pair with radially outwardly extending fields, and further comprising a member of good magnetic permeability embodied by said end bearing, and a magnet wheel magnetically coupled to said arbor and connected to said dial train.

13. Apparatus as defined in claim 12, wherein said magnet wheel lies in a common plane with said index wheel and is separated from the latter by a small distance, and the diameter of said index wheel exceeds that of said arbor by between threeand thirty-hundredths of a millimeter.

14. Apparatus as defined in claim 1, wherein said brush comprises between about l0 and 40 bristles arranged approximately in a common plane and distributed uniformly about a part of the index wheel circumference, the number of said bristles divided into the number of index wheel teeth covered by said brush not yielding a quotient that approaches an integral number.

15. Apparatus as defined in claim 1, for a wristwatch, wherein said index wheel has a diameter of between about 0.4 and 1 mm., and a thickness of between about 0.3 and 0.05

16. Apparatus as defined in claim 1, for a wristwatch, wherein the diameter of said bristles is not greater than onehundredth of a millimeter.

17. Apparatus as defined in claim 1, for a wristwatch, wherein said bristles are made of tungsten wire.

18. Apparatus as defined in claim 1, for s wristwatch, wherein said bristles are made of glass.

19. Apparatus as defined in claim I, for a wristwatch, wherein said bristles are made chiefly of animal organs.

20. Apparatus as defined in claim 21, wherein said bristles are made from insect hairs.

21. Apparatus as defined in claim 4, wherein said arbor has a plurality of pairs of alternating polarity on its circumference.

22. A ratchet mechanism for transforming a mechanical oscillation into a continuous rotary motion, with a ratchet wheel, a pawl engaging the teeth of the ratchet wheel on one side and a transmission member coupled to the ratchet wheel, for watches having an audio frequency mechanical oscillator as regulator, which is connected to the clockwork through the ratchet mechanism and the transmission member, said ratchet wheel being a relatively wide toothed drum, and said pawl being provided with a jewel having an edge which cooperates with the teeth of said ratchet wheel.

23. A ratchet mechanism according to claim 22, wherein an approximately parellelipipedic pawl jewel is arranged on the driving pawl in such a fashion that a diagonal of the pawl jewel lies in the direction of the pawl, so that a corner edge of the pawl jewel comes into contact with the flanks of the teeth of the ratchet wheel.

24. A ratchet mechanism according to claim 22, wherein a triangular prismatic pawl jewel is arranged on the driving pawl in such a manner that the corner edge of the jewel is directed towards the flanks of the teeth of the ratchet wheel.

25. A ratchet mechanism according to claim 22, wherein the ratchet wheel is mounted sn a pivot made of a material having a high magnetic coercive force, this pivot being either simply magnetized through and through or having around its circumference pairs of magnetic poles of alternating polarity, and said pivot being magnetically coupled with a pole wheel forming the transmission member.

26. A ratchet mechanism according to claim 25, wherein the ratchet wheel is overhung on the pivot made of material having a high magnetic coercive force, and in that the pivot supported on one side is secured against axial movement by a magnetically active and bearing.

27. A ratchet mechanism according to claim 26, wherein the end bearing of the pivot is provided with a piece of magnetically soft material. 

1. Apparatus for converting a mechanical vibration into a unidirectional rotary movement, particularly suitable for timepieces of the type having as the regulating organ a mechanical resonator operating at an audio frequency connected to a dial train, comprising a toothed index wheel having teeth with gently sloping backs and steep contact faces, a pawl coacting with said teeth, a brush comprising a plurality of bristles that rest on a plurality of said teeth backs and are directed towards, and cooperate with, said teeth contact faces, a mechanical resonator operative at an audio frequency, said pawl being connected to said mechanical resonator to turn said index wheel step by step in a desired direction and said brush being arranged with respect to said index wheel so as to offer negligible resistance to angular displacement of said wheel in the desired direction but substantially to prevent angular displacement thereof in the opposite direction, a dial train magnetically coupled to said index wheel, an arbor of high magnetic retentivity for said index wheel, said index wheel being mounted to overhand on said arbor, and a magnetic end bearing for magnetically preventing axial movement of said arbor.
 2. Apparatus as defined in claim 1, further comprising magnetic pole pairs on said index wheel with alternating polarity around the wheel circumference and radially outwardly extending fields, and a magnet wheel magnetically coupled to said index wheel.
 3. Apparatus as defined in claim 2, wherein said index wheel has two or three pole pairs.
 4. Apparatus as defined in claim 1, wherein said arbor is radially magnetized to have one pole pair, and a magnet wheel magnetically coupled to said arbor.
 5. Apparatus as defined in claim 1, wherein said brush bristles make an average angle of 100* to 140*, with The radius of said index wheel at the points of contact between said bristles and said index wheel.
 6. Apparatus as defined in claim 5, wherein said brush bristles converge.
 7. Apparatus as defined in claim 1, wherein the entirety of the bristle ends define part of a virtually circular cylinder having a diameter approximately equal to the mean diameter of said index wheel.
 8. Apparatus as defined in claim 7, wherein said brush covers about half of all of the index wheel teeth.
 9. Apparatus as defined in claim 1, wherein said brush covers at least two teeth of said index wheel.
 10. Apparatus as defined in claim 1, further comprising a substantially rectangular parallelepiped stone so arranged on said pawl means that a diagonal of said stone is directed towards said pawl, whereby a corner of said stone cooperates with said contact face of an index wheel tooth.
 11. Apparatus as defined in claim 1, further comprising a triangular-prism stone so arranged on said pawl that a corner edge of said stone is directed towards, and contacts the teeth of said index wheel.
 12. Apparatus as defined in claim 1, wherein said arbor is magnetized to have at least one pole pair with radially outwardly extending fields, and further comprising a member of good magnetic permeability embodied by said end bearing, and a magnet wheel magnetically coupled to said arbor and connected to said dial train.
 13. Apparatus as defined in claim 12, wherein said magnet wheel lies in a common plane with said index wheel and is separated from the latter by a small distance, and the diameter of said index wheel exceeds that of said arbor by between three- and thirty-hundredths of a millimeter.
 14. Apparatus as defined in claim 1, wherein said brush comprises between about 10 and 40 bristles arranged approximately in a common plane and distributed uniformly about a part of the index wheel circumference, the number of said bristles divided into the number of index wheel teeth covered by said brush not yielding a quotient that approaches an integral number.
 15. Apparatus as defined in claim 1, for a wristwatch, wherein said index wheel has a diameter of between about 0.4 and 1 mm., and a thickness of between about 0.3 and 0.05 mm.
 16. Apparatus as defined in claim 1, for a wristwatch, wherein the diameter of said bristles is not greater than one-hundredth of a millimeter.
 17. Apparatus as defined in claim 1, for a wristwatch, wherein said bristles are made of tungsten wire.
 18. Apparatus as defined in claim 1, for s wristwatch, wherein said bristles are made of glass.
 19. Apparatus as defined in claim 1, for a wristwatch, wherein said bristles are made chiefly of animal organs.
 20. Apparatus as defined in claim 21, wherein said bristles are made from insect hairs.
 21. Apparatus as defined in claim 4, wherein said arbor has a plurality of pairs of alternating polarity on its circumference.
 22. A ratchet mechanism for transforming a mechanical oscillation into a continuous rotary motion, with a ratchet wheel, a pawl engaging the teeth of the ratchet wheel on one side and a transmission member coupled to the ratchet wheel, for watches having an audio frequency mechanical oscillator as regulator, which is connected to the clockwork through the ratchet mechanism and the transmission member, said ratchet wheel being a relatively wide toothed drum, and said pawl being provided with a jewel having an edge which cooperates with the teeth of said ratchet wheel.
 23. A ratchet mechanism according to claim 22, wherein an approximately parellelipipedic pawl jewel is arranged on the driving pawl in such a fashion that a diagonal of the pawl jewel lies in the direction of the pawl, so that a corner edge of the pawl jewel comes into contact with the flanks of the teeth of the ratchet wheel.
 24. A ratchet mechanism according to claim 22, wherein a triangular prismatic pawl jewel is arranged on the driving pawl in such a manner thaT the corner edge of the jewel is directed towards the flanks of the teeth of the ratchet wheel.
 25. A ratchet mechanism according to claim 22, wherein the ratchet wheel is mounted sn a pivot made of a material having a high magnetic coercive force, this pivot being either simply magnetized through and through or having around its circumference pairs of magnetic poles of alternating polarity, and said pivot being magnetically coupled with a pole wheel forming the transmission member.
 26. A ratchet mechanism according to claim 25, wherein the ratchet wheel is overhung on the pivot made of material having a high magnetic coercive force, and in that the pivot supported on one side is secured against axial movement by a magnetically active and bearing.
 27. A ratchet mechanism according to claim 26, wherein the end bearing of the pivot is provided with a piece of magnetically soft material. 